Synthesis of Multicolor Core/Shell NaLuF₄:Yb3+/Ln3+@CaF₂ Upconversion Nanocrystals

Recent advances in design of lanthanide-containing NIR-II luminescent nanoprobes

Luminescent biosensing in the second near-infrared window (NIR-II, 1000-1700 nm) region, which has weak tissue scattering and low autofluorescence, draws extensive attention owing to its deep tissue penetration, good spatial resolution and high signal-to-background ratio. As a new generation of NIR-II probes, lanthanide (Ln3+)-containing nanoprobes exhibit several superior properties. With the rapid development of Ln3+-containing NIR-II nanoprobes, many significant advances have been accomplished in their optical properties tuning and surface functional modification for further bioapplications. Rather than being exhaustive, this review aims to survey the recent advances in the design strategies of inorganic Ln3+-containing NIR-II luminescent nanoprobes by highlighting their optical performance optimization and surface modification approaches. Moreover, challenges and opportunities for this kind of novel NIR-II nanoprobes are envisioned.

Delivery of drugs, proteins, and nucleic acids using inorganic nanoparticles

Inorganic nanoparticles provide multipurpose platforms for a broad range of delivery applications. Intrinsic nanoscopic properties provide access to unique magnetic and optical properties. Equally importantly, the structural and functional diversity of gold, silica, iron oxide, and lanthanide-based nanocarriers provide unrivalled control of nanostructural properties for effective transport of therapeutic cargos, overcoming biobarriers on the cellular and organismal level. Taken together, inorganic nanoparticles provide a key addition to the arsenal of delivery vectors for fighting disease and improving human health.

Recent advances of lanthanide-doped upconversion nanoparticles for biological applications

Near infrared (NIR) excited lanthanide-doped upconversion nanoparticles (UCNPs) are emerging as a new type of fluorescent tag for biological applications, which can emit multi-photon ultraviolet, visible or NIR luminescence for imaging or activation of photosensitive molecules. Here, we present a comprehensive review on recent advances of UCNPs for a manifold of biological applications, including upconversion mechanisms, building bright multicolor upconversion nanocrystals, single nanoparticle and super resolution imaging, in vivo optical and multimodal imaging, photodynamic therapy, light-controlled drug release, biosensing, and toxicities. Our perspectives on the future development of UCNPs are also described.

Optogenetics sheds new light on tissue engineering and regenerative medicine

Optogenetics has demonstrated great potential in the fields of tissue engineering and regenerative medicine, from basic research to clinical applications. Spatiotemporal encoding during individual development has been widely identified and is considered a novel strategy for regeneration. A as a noninvasive method with high spatiotemporal resolution, optogenetics are suitable for this strategy. In this review, we discuss roles of dynamic signal coding in cell physiology and embryonic development. Several optogenetic systems are introduced as ideal optogenetic tools, and their features are compared. In addition, potential applications of optogenetics for tissue engineering are discussed, including light-controlled genetic engineering and regulation of signaling pathways. Furthermore, we present how emerging biomaterials and photoelectric technologies have greatly promoted the clinical application of optogenetics and inspired new concepts for optically controlled therapies. Our summation of currently available data conclusively demonstrates that optogenetic tools are a promising method for elucidating and simulating developmental processes, thus providing vast prospects for tissue engineering and regenerative medicine applications.

Lanthanide-Doped Upconversion Nanocarriers for Drug and Gene Delivery

Compared to traditional cancer treatments, drug/gene delivery is an advanced, safe, and efficient method. Nanoparticles are widely used as nanocarriers in a drug/gene delivery system due to their long circulation time and low multi-drug resistance. In particular, lanthanide-doped upconversion nanoparticles (UCNPs) that can emit UV and visible light by near-infrared (NIR) upconversion demonstrated more efficient and safer drug/gene delivery. Because of the low penetration depth of UV and visible light, a photoinduced reaction such as photocleavage or photoisomerization has proven restrictive. However, NIR light has high tissue penetration depth and stimulates the photoinduced reaction through UV and visible emissions from lanthanide-doped UCNPs. This review discusses the optical properties of UCNPs that are useful in bioapplications and drug/gene delivery systems using the UCNPs as a photoreaction inducer.

The theoretical molecular weight of NaYF 4 :RE upconversion nanoparticles

Upconversion nanoparticles (UCNPs) are utilized extensively for biomedical imaging, sensing, and therapeutic applications, yet the molecular weight of UCNPs has not previously been reported. Herein, we present a theory based upon the crystal structure of UCNPs to estimate the molecular weight of UCNPs: enabling insight into UCNP molecular weight for the first time. We estimate the theoretical molecular weight of various UCNPs reported in the literature, predicting that spherical NaYF4 UCNPs ~ 10 nm in diameter will be ~1 MDa (i.e. 106 g/mol), whereas UCNPs ~ 45 nm in diameter will be ~100 MDa (i.e. 108 g/mol). We also predict that hexagonal crystal phase UCNPs will be of greater molecular weight than cubic crystal phase UCNPs. Additionally we find that a Gaussian UCNP diameter distribution will correspond to a lognormal UCNP molecular weight distribution. Our approach could potentially be generalised to predict the molecular weight of other arbitrary crystalline nanoparticles: as such, we provide stand-alone graphic user interfaces to calculate the molecular weight both UCNPs and arbitrary crystalline nanoparticles. We expect knowledge of UCNP molecular weight to be of wide utility in biomedical applications where reporting UCNP quantity in absolute numbers or molarity will be beneficial for inter-study comparison and repeatability.

Neto E, Mazali IO, Murugesu M, Sigoli FA. One pot synthesis and systematic study of the photophysical and magnetic properties and thermal sensing of α and β-phase NaLnF4 and β-phase core@shell nanoparticles

Hierarchical nanostructured nanoparticles showing high values of relative thermal sensitivity and magnetization at low temperatures.

BaCaLu2F10:Ln3+ (Ln = Eu, Dy, Tb, Sm, Yb/Er, Yb/Ho) spheres: ionic liquid-based synthesis and luminescence properties

Alkaline earth metal rare earth fluoride BaCaLu₂F₁₀:Ln³⁺ (Ln = Eu, Dy, Tb, Sm, Yb/Er, Yb/Ho) submicrospheres with uniform morphology and size were synthesized via a facile ionic liquid-based hydrothermal route. The down- and up-conversion luminescence has been investigated.

Controlled Synthesis of Monodisperse Hexagonal NaYF₄:Yb/Er Nanocrystals with Ultrasmall Size and Enhanced Upconversion Luminescence

The ability to synthesize upconversion nanocrystals (UCNCs) with tailored upconversion luminescence and controlled size is of great importance for biophotonic applications. However, until now, limited success has been met to prepare bright, ultrasmall, and monodispersed β-NaYF₄:Yb³⁺/Er³⁺ UCNCs. In this work, we report on a synthetic method to produce monodisperse hexagonal NaYF₄:Yb³⁺/Er³⁺ nanocrystals of ultrasmall size (5.4 nm) through a precise control of the reaction temperature and the ratio of Na⁺/Ln³⁺/F⁻. We determined the optimum activator concentration of Er³⁺ to be 6.5 mol % for these UCNCs, yielding about a 5-fold higher upconversion luminescence (UCL) intensity than the commonly used formula of NaYF₄:30% Yb³⁺/2% Er³⁺. Moreover, a thin epitaxial shell (thickness, 1.9 nm) of NaLnF₄ (Ln = Y, Gd, Lu) was grown onto these ultrasmall NaYF₄:Yb³⁺/Er³⁺ NCs, enhancing its UCL by about 85-, 70- and 50-fold, respectively. The achieved sub-10-nm core and core–shell hexagonal NaYF₄:Yb³⁺/Er³⁺ UCNCs with enhanced UCL have strong potential applications in bioapplications such as bioimaging and biosensing.